The publications and other materials used herein to illuminate the background of the invention, and in particular, cases to provide additional details respecting the practice, are incorporated by reference.
VAP-1 is a human endothelial cell adhesion molecule that has several unique properties that distinguish it from the other inflammation-related adhesion molecules. It has a unique and restricted expression pattern and mediates lymphocyte binding to vascular endothelium (Salmi, M., and Jalkanen, S., Science 257:1407-1409 (1992)). Inflammation induces the upregulation of VAP-1 to the surface of vascular endothelial cells mediating leukocyte entry to skin, gut and, inflamed synovium (Salmi, M., and Jalkanen, S., Science 257:1407-1409 (1992); Salmi, M, et al., J. Exp. Med. 178:2255-2260 (1993); Arvilommi, A., et al., Eur. J. Immunol. 26:825-833 (1996); Salmi, M., et al., J. Clin. Invest. 99:2165-2172 (1997): (Salmi. M., and Jalkanen, S., J. Exp. Med. 183:569-579 (1996); J. Exp. Med 186:589-600 (1997)). One of the most interesting features of VAP-1 is a catalytic extracellular domain which contains a monoamine oxidase activity (Smith, D. J., et al., J. Exp. Med 188:17-27 (1998)).
The cloning and sequencing of the human VAP-1 cDNA revealed that it encodes a transmembrane protein with homology to a class of enzymes called the copper-containing amine oxidases (E.C. 1.4.3.6). Enzyme assays have shown that VAP-1 possesses a monoamine oxidase (MAO) activity which is present in the extracellular domain of the protein (Smith, D. J., et al., J. Exp. Med 188:17-27 (1998)). Thus, VAP-1 is an ecto-enzyme. Analysis of the VAP-1 MAO activity showed that VAP-1 belongs to the class of membrane-bound MAO's termed semicarbazide-sensitive amine oxidases (SSAO). These are distinguished from the widely distributed mitochondrial MAO-A and B flavoproteins by amino acid sequence, cofactor, substrate specificity and sensitivity to certain inhibitors. However, certain substrates and inhibitors are common to both SSAO and MAO activities.
Leukocyte trafficking from blood to tissues is not only a prerequisite for generating normal immune responses against microbes but it is also needed for immunosurveillance against malignantly transformed cells. Normally leukocytes leave the blood using a multistep extravasation cascade involving many activation and adhesion molecules both on the leukocyte and on the endothelial lining. VAP-1 is one endothelial molecule that supports rolling, firm adhesion, and transmigration of various subsets of leukocytes into sites of inflammation (Salmi, M., and S. Jalkanen. 2005. Nat. Rev. Immunol. 5:760-771). VAP-1 belongs to semicarbazide sensitive amine oxidases, which are enzymes that catalyze oxidative deamination of amines into corresponding aldehydes in a reaction that also produces hydrogen peroxide and ammonium. The adhesive role of VAP-1 in leukocyte trafficking can be inhibited using function-blocking mAbs or enzyme inhibitors in multiple in vitro and in vivo inflammation models (Salmi, M., and S. Jalkanen. 2005. Nat. Rev. Immunol. 5:760-771). The anti-VAP-1 antibodies do not inhibit the enzymatic activity of VAP-1, and the enzyme inhibitors do not alter the mAb-defined surface epitopes of VAP-1 (Koskinen, K., P. J. Vainio, D. J. Smith, M. Pihlavisto, S. Yla-Herttuala, S. Jalkanen, and M. Salmi. 2004. Blood 103:3388-3395; Bonder, C., M. G. Swain, L. D. Zbytnuik, M. U. Norman, J. Yamanouchi, P. Santamaria, M. Ajuebor, M. Salmi, S. Jalkanen, and P. Kubes. 2005. Immunity 23:153-163). It is thus thought that VAP-1 is involved in leukocyte extravasation by serving as a traditional adhesion molecule (mAb-defined epitopes) and as an enzyme (by reacting with surface displayed amines of leukocytes) (Salmi, M., and S. Jalkanen. 2005. Nat. Rev. Immunol. 5:760-771).
Various strategies for inhibiting VAP-1 activity have been disclosed. For example, WO 93/25582 discloses a monoclonal antibody specifically binding to VAP-1. WO 2003/093319 describes a humanized anti-VAP-1 monoclonal antibody.
Alternatively, VAP-1 can be counteracted by using small molecules as inhibitors. The patent publications WO 2002/020290, WO 2002/002541, WO 2003/006003 and WO 2005/080319 disclose certain hydrazino compounds useful as specific VAP-1 SSAO inhibitors that modulate VAP-1 activity. These compounds are described as useful for the treatment of acute and chronic inflammatory conditions or diseases as well as diseases related to carbohydrate metabolism, aberrations in adipocyte differentiation or function and smooth muscle cell function, and various vascular diseases.
WO 2006/128951 discloses the conjugation of a small molecule inhibitor to a peptide capable of binding to VAP-1, where the peptide has a sequence of 7 to 9 amino acids, and where at least one lysine residue is located in the mid-portion of the sequence.